The use of cardioplegic arrest has markedly improved the results of cardiac surgery for a variety of conditions. Most surgeons agree that the best cardioplegic solution has not been found despite a large amount of clinical and experimental work. This is evident from the many different solutions being used clinically. The best solution would be one that offered complete protection of myocardial function and metabolism for the longest time at a given temperature. To date, the majority of studies in this area have employed an empirical approach and suffer from a lack of adequate controls, a multiplicity of variables and lack of confirmation in a hypertrophied model. We plan to study the effect of single variables on myocardial preservation using the working rat heart model. After determining the optimal temperature, pH and osmolarity of cardioplegic solutions, we will evaluate the effect of single additions: glucose, calcium, propranolol, adenosine and local anesthetics. While evaluating the effects of these solutions on myocardial function (ventricular pressure, coronary flow, left atrial pressure and cardiac output), we will also investigate the metabolic changes which occur after cardioplegic arrest; specifically changes in oxygen consumption, glucose utilization and protein turnover. The efficacy of promising solutions will be further tested using a hypertrophied model. An understanding of both the functional and metabolic changes wrought by ischemia and cardioplegia should allow a more rational approach to the problem of limiting ischemic injury during cardiac surgery.